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Application of vehicle dynamics XYZ domain fusion based on intelligent chassis

Publish Date: 2022.12.01

The electrification of the chassis is closely related to the electrification of the whole vehicle. The intelligent chassis essentially serves the dynamic experience of drivers and passengers.

On November 18, 2022, at the 2022 Second Automobile Intelligent Chassis Conference, sponsored by Geshi Automobile, under the guidance of Shanghai Hongqiao International Central Business District Management Committee and Shanghai Minhang District People's Government, and co organized by Shanghai Nanhongqiao Investment and Development (Group) Co., Ltd., Zhang Lunwei, director of Geely Automobile Central Research Institute, said:

Geely believes that the development of chassis is essentially the integration control of XYZ in three directions, and the ultimate goal of intelligent chassis is to improve the user experience and solve the functional requirements of scenarios.

基于智能底盘的车辆动力学XYZ域融合应用实践

Zhang Lunwei | Director of Geely Automobile Central Research Institute

The following is the content of the speech:

Geely Automobile Central Research Institute serves all sub brands of Geely Automobile. Today, we mainly share our domain integration application practice of vehicle dynamics XYZ based on intelligent chassis.

Industry development direction of intelligent chassis

In our opinion, the final development direction of chassis is around intelligent chassis. Based on this, Geely Automobile has carried out a lot of research and application in intelligent chassis, electronic control and electrification of chassis.

Among them, the electrification of the chassis is closely related to the electrification of the whole vehicle. The essence of chassis intelligence is to serve the dynamic experience of drivers and passengers. The so-called dynamic experience is essentially the action of XYZ in three directions. From this perspective, we believe that the essence of chassis development is to integrate and control the three directions of XYZ, so as to improve the user experience and solve the functional requirements of scenarios.

As a OEMs, this is our core requirement. Essentially, OEMs only want to do one thing, that is, to differentiate the functional experience. However, suppliers provide the same thing to different OEMs. So how to create differentiation, OEMs need to do top-level development. This is why we want to do domain level control, top-level control, and also hope that the supplier's scheme is white box, Reasons for providing standardized interfaces.

In addition, why does the rise of domestic supply chain bring huge opportunities to OEMs. Take hardware as an example. In the past, there were no active shock absorbers, they were all passive shock absorbers, and there was no intelligent braking system. They were all mechanical hydraulic braking systems. The emergence of intelligent wire control and electronic control systems makes the industry begin to attach importance to functional innovation and redundant control. Based on these priorities, we can carry out in-depth cooperation with the domestic supply chain. Like the overtaking of electric vehicles, the intelligent chassis will become the next corner overtaking point.

The user's demand for dynamic performance in driving can be divided into many stages. Geely has also introduced different versions of the chassis domain control. We have accumulated a lot of experience and models in the domain control version 1.0. In terms of domain control, Geely's planning is from distributed control, global integration to central integration, which is currently at the stage of global integration control.

Opportunities of vehicle dynamics on intelligent chassis

In the previous stage, we mainly focused on the hardware field, such as the active suspension, electric drive control, and aerodynamics package in the line control system. However, we gradually found that the intelligent chassis has brought more opportunities for vehicle dynamics.

The essence of vehicle dynamics is to solve the relationship between various forces, especially the force on the tire pavement system and the 6-DOF action of the vehicle body after the force. The core principles of integrated control are two: effective control and functional compensation.

基于智能底盘的车辆动力学XYZ域融合应用实践

Photo source: Geely Automobile Central Research Institute

For example, imagine driving on opposite roads (roads with different adhesion coefficients for wheels). Although ESC is available, it is sometimes difficult for people to control the stability of the vehicle. If steering by wire is used, active steering intervention can be set on the wheels to make steering control more effective.

In essence, we have three main goals for chassis domain control: first, safety and stability. Whether it is the braking system or the steering system, safety and stability are paramount. The second is the handling performance. The third is the comfort. These three dimensions are also the long-term goals of intelligent chassis.

We believe that the essence of chassis development is to integrate the three directions of XYZ, which is an unchanging trend. At the same time, functional decoupling, software and hardware decoupling are also major development directions. Combined with two points, Geely's strategy is to solve the dynamic control of the vehicle, and achieve functional decoupling and soft and hard decoupling at the same time.

At present, the essence of various functions of the intelligent chassis is based on the joint action of hardware and software. There are many ways to achieve these functions: for example, to maintain vehicle stability on the open circuit surface, you can rely on steering by wire. At this time, whether it is relying on functional backup or functional redundancy, the ultimate goal is to improve the driver's experience, based on the principle of experience first.

Speaking of redundancy, when we are doing the chassis domain control version 1.0 and version 2.0, we consider less system engineering in version 1.0. The control is mainly vertical control. The domain control version 2.0 is mainly used to distinguish the relationship between various functions and hardware. Function decoupling is precisely for this purpose.

To achieve decoupling, we need to consider a lot when building system functions, including how to consider redundancy and how to realize the principle of experience first.

We have adopted two ways to build the system. One is the gateway type from the system to the architecture. The feature is that the sensor signal will be transmitted to the ECU of each actuator, and then centralized to the central controller for decision-making. This is the gateway type domain control of version 1.0.

The other is centralized control, which adopts the mode of "central integration+distribution". We believe that this mode will be the mainstream in the next four to five years. Adherence to this approach can achieve the effect of the OEMs and suppliers performing their own duties and combining strength, and can solve the problem of cooperation between suppliers and OEMs.

Geely's vehicle dynamics XYZ fusion strategy

When it comes to Geely's vehicle dynamics XYZ integration strategy, we need to recall the three goals of "safety, performance and comfort". From the perspective of safety, we need to ensure that the vehicle is safe and controllable under critical or extreme conditions, especially to ensure the stability and robustness of the vehicle under various harsh scenarios.

From the performance point of view, the vehicle needs to have higher lateral acceleration, and the change rate of understeer degree should be reduced as much as possible. It has a larger linear range of understeer, a higher vehicle limit, and a higher tracking ability; From the comfort point of view, it is necessary to reduce energy damage. The system operation should avoid causing the drivers and passengers' sense of tension and danger as much as possible, so that the vehicle can be driven more easily, even in special and severe scenes.

In addition to the strategy layer, let's share our application practices in the development process. From VDSW to ICC, we have always followed the principle of user tasks and experience needs first, and continued to promote the iteration of algorithms and functions. Among them, we found that establishing a user scenario library and digitizing it is an effective means to support the development and verification of domain algorithms.

At this stage, Geely adopts the architecture model shown in the figure below. It conducts domain integration development by applying 3-tier and multi-layer layout, which has four advantages: fault tolerance, extensibility, flexibility and modularity.

基于智能底盘的车辆动力学XYZ域融合应用实践

Photo source: Geely Automobile Central Research Institute

We believe that domain control should still be implemented jointly by suppliers and OEMs, which is why Geely adheres to the "centralized+distributed" path. Based on a large amount of real vehicle data, OEMs understand terminal needs better, while the supply chain is better at bottom level implementation, and has a say in security and redundancy. This way can maximize benefits.

Example of y/x integration application

Next, let's give an example. The first example is y/x integration, which mainly refers to the cooperation between active rear wheel steering and ESC. The following figure is an example of Geely's solution. By setting up DIL laboratory and combining HIL equipment such as driving simulator, shock absorber, brake, etc., a closed loop system is formed. Based on this system, the virtual calibration work in the early stage of algorithm development is realized. With these equipment, the algorithm can be optimized in the virtual simulation link.

基于智能底盘的车辆动力学XYZ域融合应用实践

Photo source: Geely Automobile Central Research Institute

The following is an exploration of how to achieve y/x integration based on the vector drive of the rear wheels, with three motors, four motors, or dual motors for the rear wheels.

Next, we will share the logical transition in the process of integration. For example, during development, deceleration can be achieved through both energy recovery and braking. How to transition between "braking" and "energy recovery"? We call it the transition problem of logic, and the essential goal of both is to slow down.

The focus of the transition problem is comfort and consistency, because when the vehicle is not calibrated properly, once it is transferred from "energy recovery" to "braking" to achieve deceleration, it will produce a strong sense of impact, which we call "logical transition is not good enough". Therefore, we need to design based on specific scenarios, list the working conditions that the vehicle will encounter, and try to realize some extreme working conditions in the simulation environment.

Example of y/z/x integration application

On Lotus models, Geely has preliminarily realized the integration control of XYZ domain, which includes active tail, electronic active stabilizer, active rear wheel steering, right rear wheel braking, CDC+air suspension, and left front wheel driving force. At the same time, it adopts air kit to balance.

In combination with the fusion practice, we have three key points to share: 1. The limit is the tire performance, and the non-linear should make good use of the tire friction circle; 2. The front and rear torque distribution can change the yaw and understeer characteristics; 3. The longitudinal, lateral and vertical directions are a coupling relationship, which can be used to change the motion state of vehicles.

基于智能底盘的车辆动力学XYZ域融合应用实践

Photo source: Geely Automobile Central Research Institute

In addition, when developing functional integration, we should also pay attention to customized design for Chinese scenes, which will become the key to win more market shares.

In a word, no matter function development or integrated application of XYZ domain, the principle of car enterprises is always "experience first". With the help of functional innovation, car enterprises and supply chains can go further on the intelligent chassis track. Finally, we also hope that China's automobile industry can fly higher, go further and go global in the trend of chassis intelligence.

(The above contents are from the keynote speech and materials of "Application Practice of Vehicle Dynamics XYZ Domain Integration Based on Intelligent Chassis" delivered by Zhang Lunwei, Minister of Geely Automobile Central Research Institute, on November 18, 2022 at the 2022 Second Automobile Intelligent Chassis Conference sponsored by Geshi Automobile, under the guidance of Shanghai Hongqiao International Central Business District Management Committee and Shanghai Minhang District People's Government, and co sponsored by Shanghai Nanhongqiao Investment and Development (Group) Co., Ltd.)

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